Protein kinases are central regulators of intracellular responses and constitute the second largest drug target class. We have developed a microwell format for displaying immobilized proteins in an aqueous medium such that separate isolated reactions can be carried out with many different proteins, substrates, or inhibitors, or binding agents in low volumes on a single microscope slide. In Phase I, we produced significant numbers of active kinases and demonstrated 20 nanoliter volume kinase assays in these microwells. In this Phase II application, we propose to extend this procedure to prepare microwell arrays of essentially the entire complement of human protein kinases and protein kinase catalytic domains, and to develop these arrays for quantitative and comprehensive inhibition assays. We will demonstrate the utility of the arrays for inhibitor specificity profiling by testing the array against a panel of known kinase inhibitors, and will perform functional characterizations of each kinase present in the array. Comprehensive kinase inhibition profiling will significantly enhance the effectiveness and efficiency of kinase drug development. [unreadable] [unreadable]